Herbicidal esters of 2-bromo-4-methylimidazole-5-carboxylic acid

ABSTRACT

A herbicidal compound having the structural formula ##STR1## where R is C 1  -C 10  alkyl; C 3  -C 8  cycloalkyl, C 3  -C 8  cycloalkylalkyl wherein the alkyl has 1 to 6 carbon atoms, C 2  -C 10  alkenyl, C 5  -C 8  cycloalkenyl; benzyl or mono- or di-substituted benzyl wherein the substituents are C 1  -C 4  alkyl, halogen, nitro or C 1  -C 4  haloalkyl and Y is substituted or unsubstituted C 1  -C 8  alkoxy, C 1  -C 8  alkylthio, C 3  -C 6  alkenyloxy, C 3  -C 6  alkenylthio, aryloxy (thio) arylalkoxy.

BACKGROUND OF THE INVENTION

Compounds having the structural formula ##STR2## wherein R is hydrogen,alkyl or substituted alkyl and Y is hydrogen, alkyl, substituted alkyl,halogen, cyano or nitro are described in U.S. Pat. No. 3,501,286 asbeing herbicides.

A compound of the formula ##STR3## is taught by Pyman and Timmis, J.Chem. Soc., pp. 494-498 (1923). However, no utility for this compound istaught other than its use as an intermediate in the preparation ofpharmaceuticals.

DESCRIPTION OF THE INVENTION

This invention relates to esters of2-bromo-4-methylimidazole-5-carboxylic acid as herbicides. The novelcompounds of this invention have the following structural formula (A)##STR4## wherein R is C₁ -C₁₀ alkyl, preferably C₂ -C₆ alkyl, morepreferably C₂ -C₅ alkyl, most preferably isopropyl, isobutyl, isopentylor sec-pentyl; C₃ -C₈ cycloalkyl, preferably C₄ -C₆ cycloalkyl, morepreferably cyclopentyl or cyclohexyl; C₃ -C₈ cycloalkylalkyl wherein thealkyl has 1 to 6 carbon atoms, preferably cyclopropylmethyl orcyclopentylmethyl; C₃ -C₁₀ alkenyl, preferably allyl or2-methyl-3-butenyl-1; C₅ -C₈ cycloalkenyl; benzyl or or di-substitutedbenzyl wherein the substituents are C₁ -C₄ alkyl, halogen, nitro or C₁-C₄ haloalkyl and Y is substituted or unsubstituted C₁ -C₈ alkoxy,preferably C₂ -C₄ alkoxy, wherein the substituent is halogen, morepreferably trichloroethoxy, C₁ -C₈ thioalkyl, preferably C₁ -C₄thioalkyl; C₃ -C₆ alkenyloxy, preferably allyloxy; C₃ -C₆ thioalkenyl,preferably thioallyl; C₆ -C₁₀ aryloxy(thio) preferably phenoxy;substituted C₆ -C₁₂ aryl alkoxy(thio), preferably benzyloxy. Suitablecompounds within the above genus are those wherein R is either C₂ -C₆alkyl or isopropyl, isobutyl or sec-pentyl and Y is C₂ -C₄ alkoxy, C₁-C₄ thioalkyl or phenoxy.

The structural formula (A) when R and Y are as defined is intended todefine compounds of either of the following two structural isomers##STR5## or mixtures of the two isomers in any proportion.

Both isomers are herbicidally active.

In the above description of the compounds of this invention alkylincludes both straight and branched configurations; for example, methyl,ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, andtert-butyl, the amyls, the hexyls, the heptyls, the nonyls and thedecyls.

The compounds of this invention are active herbicides of a general type.That is, they are herbicidally effective against a wide range of plantspecies. The method of controlling undesirable vegetation of the presentinvention comprises applying an herbicidally effective amount of theabove-described compounds to the area where control is desired.

The compounds of the present invention can be prepared by the followinggeneral method. ##STR6## wherein R is as defined and TEC is atransesterification catalyst such as Ti(O-alkyl)₄, preferablyTi(isopropoxy)₄. ##STR7## wherein R is as defined, ##STR8## is ahaloformate or a halothioformate wherein Y is as defined and X ischlorine.

Generally, for step (1) at least one mole of the alcohol is used for thereaction with the ethyl ester to prepare the imidazoles. Preferably, aslight mole excess of the alcohol is used. The reaction mixture isrefluxed until completion of the reaction. The reaction product isrecovered by removing the volatile materials. Atmospheric,subatmospheric or superatmospheric pressures can be used, depending onthe boiling point of the solvent used. Ethanol is conveniently strippedat elevated temperatures and reduced pressure.

Reaction step (2) is run in a solvent such as tetrahydrofuran, at atemperature of about 25°, preferably room temperature, using equal moleamounts of the two reactants and a hydride base. Preferably, the hydridebase is sodium hydride.

The reaction product is a mixture of (1) and (3) isomers and is workedup by conventional techniques.

The following example teaches the synthesis of a representative compoundof this invention.

EXAMPLE I Isopropyl ester of 2-Bromo-4-methyl-5-imidazolecarboxylic acid##STR9##

To a suspension of 6.4 grams (g) (2.7×10⁻² moles) ofethyl-2-bromo-4-methyl-5-imidazole carboxylate in 70 milliliters (ml)isopropanol was added 0.6 ml (2.4×10⁻³ moles) tetraisopropyl titanate.The resulting mixture was heated to reflux for 3 days, then concentratedin vacuo to one-half the original volume. The solution was cooled on iceand the precipitated crystalline solid was filtered and air dried togive 3.4 g of the desired product.

EXAMPLE II Ethyl ester of 1- and3-(S-Methylthioformyl)-2-bromo-4-methylimidazolecarboyxlic acid##STR10##

To a suspension of 257 milligrams (mg) (1.07×10⁻² moles) of sodiumhydride in 20 ml of anhydrous tetrahydrofuran was added, in portions, 2g (8.58×10⁻³ moles) of the ethyl ester of2-bromo-4-methyl-5-imidazolecarboxylate. The resulting suspension wascooled to 0° C. and 858 ul (8.58×10⁻³ moles) of methylthiochloroformatewas added dropwise. The reaction mixture was stirred overnight at roomtemperature. The precipitated sodium chloride was removed by filtrationand concentration of the filtrate in vacuo gave 2.1 g (81%) of ethyl 1-and 3-(S-methylthioformyl)-2-bromo-4-methyl-5-imidazolecarboxylate as adark oil.

The following is a table of certain selected compounds that arepreparable according to the procedure described herein. Compound numbersare assigned to each compound and are used throughout the remainder ofthe application.

                  TABLE I                                                         ______________________________________                                         ##STR11##                                                                    Compound                                                                      Number  R             Y           m.p. °C.                             ______________________________________                                        1       ethyl         Sn-propyl   yellow oil                                  2       ethyl         Sethyl      yellow oil                                  3       isopropyl     Sn-propyl   yellow oil                                  4       ethyl         Smethyl     yellow oil                                  5       isopropyl     Smethyl     yellow oil                                  6       isopropyl     Sn-butyl    orange oil                                  7       isopropyl     Sisopropyl  yellow oil                                  8       ethyl         Sn-butyl    dark oil                                    9       ethyl         Si-propyl   yellow oil                                  10      isopropyl     Sethyl      yellow oil                                  11      isobutyl      Smethyl     yellow oil                                  12      sec-butyl     Smethyl     yellow oil                                  13      cyclopentyl   Smethyl     yellow oil                                  14      allyl         Smethyl     yellow oil                                  15      n-butyl       Smethyl     dark oil                                    16      n-propyl      Smethyl     dark oil                                    17      2-(5-methylpentyl)                                                                          Smethyl     dark oil                                    18      sec-pentyl    Smethyl     yellow oil                                  19      isopropyl     ethoxy      yellow oil                                  20      ethyl         ethoxy      63-64                                       21      isopropyl     OCH.sub.2 CCl.sub.3                                                                       colorless oil                               22      isopropyl     n-butoxy    colorless oil                               23      ethyl         n-butoxy    colorless oil                               24      ethyl         allyloxy    waxy solid                                  25      ethyl         OCH.sub.2 CCl.sub.3                                                                       tan solid                                   26      isopropyl     phenoxy     yellow oil                                  27      sec-butyl     OCH.sub.2 CCl.sub.3                                                                       orange oil                                  28      sec-butyl     benzyloxy   yellow oil                                  ______________________________________                                    

Herbicidal Screening Tests

As previously mentioned, the herein described compounds produced in theabove-described manner are phytotoxic compounds which are useful andvaluable in controlling various plant species. Selected compounds ofthis invention were tested as herbicides in the following manner.

Pre-emergence herbicide test. On the day preceding treatment, seeds ofeight different weed species are planted in loamy sand soil inindividual rows using one species per row across the width of a flat.The seeds used are green foxtail (FT) (Setaria viridis), watergrass (WG)(Echinochloa crusgalli), wild oat (WO) (Avena fatua), annualmorningglory (AMG) (Ipomoea lacunosa), velvetleaf (VL) (Abutilontheophrasti), Indian mustard (MD) (Brassica juncea), curly dock (CD)(Rumex crispus), and yellow nutsedge (YNG) (Cyperus esculentus). Ampleseeds are planted to give about 20 to 40 seedlings per row, afteremergence, depending upon the size of the plants.

Using an analytical balance, 600 milligrams (mg) of the compound to betested are weighed out on a piece of glassine weighing paper. The paperand compound are placed in a 60 milliliter (ml) wide-mouth clear bottleand dissolved in 45 ml of acetone or substituted solvent. Eighteen ml ofthis solution are transferred to a 60 ml wide-mouth clear bottle anddiluted with 22 ml of a water and acetone mixture (19:1) containingenough polyoxyethylene sorbitan monolaurate emulsifier to give a finalsolution of 0.5% (v/v). The solution is then sprayed on a seeded flat ona linear spray table calibrated to deliver 80 gallons per acre (748L/ha). The application rate is 4 lb/acre (4.48 Kg/ha).

After treatment, the flats are placed in the greenhouse at a temperatureof 70° to 80° F. and watered by sprinkling. Two weeks after treatment,the degree of injury or control is determined by comparison withuntreated check plants of the same age. The injury rating from 0 to 100%is recorded for each species as percent control with 0% representing noinjury and 100% representing complete control.

The results of the tests are shown in the following Table II.

                  TABLE II                                                        ______________________________________                                        Pre-Emergence Herbicidal Activity                                             Application Rate - 4.48 kg/ha                                                 Cmpd.                                                                         No.   FT     WG     WO    AMG   VL   MD   CD   YNG                            ______________________________________                                         1     0      0      0     0     0    0    0   0                               2     0      0      0     0     0    0    0   0                               3    90     90     80    60    90   90   100  0                               4     0      0      0     0    60   60    0   0                               5    100    100    90    80    100  100  90   0                               6    100    90     80    100   100  100  80   30                              7    90     90     60    100   100  100  85   10                              8    20     20     20    60    60   60   80   60                              9     0      0     10    20     0    0   100  0                              10    100    100    40    60    100  100  60   10                             11     0      0      0     0     0    0    0   0                              12    100    100    85    100   100  100  70   0                              13    25     100    70    60    100  100  100  0                              14    80     90     70    100   95   100  80   0                              15    10     75     60     0    100  100  40   0                              16    90     90     65    70    100  100  100  0                              17     0     60      0     0     0    0   20   0                              18    40     30      0    20    100  100  90   0                              19    100    100    80    100   100  100  80   0                              20    20      0      0    40     0    0   80   0                              21    100    100    90    100   100  100  100  0                              22    100    100    60    100   100  100  100  0                              23     0      0      0     0     0    0    0   0                              24     0      0      0     0     0    0    0   0                              25     0      0      0     0     0    0    0   0                              26    100    100    90    100   100  100  90   0                              27    85     100    20     0    70   95   60   0                              28    --     --     --    --    --   --   --   --                             ______________________________________                                         -- = Not tested.                                                         

Post-Emergence Herbicide Test: This test is conducted in an identicalmanner to the testing procedure for the pre-emergence herbicide test,except the seeds of the eight different weed species are planted 10-12days before treatment. Also, watering of the treated flats is confinedto the soil surface and not to the foliage of the sprouted plants.

The results of the post-emergence herbicide test are reported in TableIII.

                  TABLE III                                                       ______________________________________                                        Post-Emergence Herbicidal Activity                                            Application Rate - 4.48 kg/ha                                                 Cmpd.                                                                         No.   FT     WG     WO    AMG   VL   MD   CD   YNG                            ______________________________________                                         1    60     40     10    40    10   60   80   0                               2    60     40     70    50    60   40   40   0                               3    100    100    100   100   100  100  100  0                               4    40     20     10    90    90   100  80   0                               5    100    100    100   90    100  100  80   20                              6    100    100    100   100   100  100  100  0                               7    100    60     40    100   100  100  85   20                              8     0      0      0    85    100  100  40   0                               9     0      0      0    85    100  100   0   20                             10    100    160    190   95    100  100  90   0                              11    90     40     40    90    90   90   60   0                              12    100    100    100   100   100  100  100  15                             13    100    100    100   85    70   100  100  10                             14    100    35     75    100   100  100  100  0                              15    100    75     60    100   80   80   70   0                              16    90     90     65    70    100  100  100  0                              17     0     60      0     0     0    0   20   0                              18    100    80     100   100   100  100  70   0                              19    100    100    100   100   100  100  95   0                              20    20     20     10    60    100  100  60   0                              21    100    100    100   100   100  100  100  0                              22    100    100    100   100   100  100  100  0                              23    90     70     10    100   80   80   100  0                              24    90     40     40    100   100  100  100  0                              25    80     20      0    80    90   60   80   0                              26    100    90     100   100   100  100  100  0                              27    85     80     55    100   100  100  100  20                             28    100    85     100   100   100  100  80   30                             ______________________________________                                    

The compounds of the present invention are useful as herbicides, and canbe applied in a variety of ways at various concentrations. In practice,the compounds herein defined are formulated into herbicidalcompositions, by admixture, in herbicidally effective amounts, with theadjuvants and carriers normally employed for facilitating the dispersionof active ingredients for agricultural applications, recognizing thefact that the formulation and mode of application of a toxicant mayaffect the activity of the materials in a given application. Thus, theseactive herbicidal compounds may be formulated as granules of relativelylarge particle size, as wettable powders, as emulsifiable concentrates,as powdery dusts, as solutions or as any of several other known types offormulations, depending upon the desired mode of application. Preferredformulations for pre-emergence herbicidal applications are wettablepowders, emulsifiable concentrates and granules. These formulations maycontain as little as about 0.5% to as much as about 95% or more byweight of active ingredient. A herbicidally effective amount dependsupon the nature of the seeds or plants to be controlled and the rate ofapplication varies from about 0.05 to approximately 25 pounds per acre,preferably from about 0.1 to about 10 pounds per acre.

Wettable powders are in the form of finely divided particles whichdisperse readily in water or other dispersants. The wettable powder isultimately applied to the soil either as a dry dust or as a dispersionin water or other liquid. Typical carriers for wettable powders includefuller's earth, kaolin clays, silicas and other readily wet organic orinorganic diluents. Wettable powders normally are prepared to containabout 5% to about 95% of the active ingredient and usually also containa small amount of wetting, dispersing, or emulsifying agent tofacilitate wetting and dispersion.

Emulsifiable concentrates are homogeneous liquid compositions which aredispersible in water or other dispersant, and may consist entirely ofthe active compound with a liquid or solid emulsifying agent, or mayalso contain a liquid carrier, such as xylene, heavy aromatic naphtha,isophorone and other non-volatile organic solvents. For herbicidalapplication, these concentrates are dispersed in water or other liquidcarrier and normally applied as a spray to the area to be treated. Thepercentage by weight of the essential active ingredient may varyaccording to the manner in which the composition is to be applied, butin general comprises about 0.5% to 95% of active ingredient by weight ofthe herbicidal composition.

Granular formulations wherein the toxicant is carried on relativelycoarse particles, are usually applied without dilution to the area inwhich suppression of vegetation is desired. Typical carriers forgranular formulations include sand, fuller's earth, bentonite clays,vermiculite, perlite and other organic or inorganic materials whichabsorb or which may be coated with the toxicant. Granular formulationsnormally are prepared to contain about 5% to about 25% of activeingredients which may include surface-active agents such as wettingagents, dispersing agents or emulsifiers; oil such as heavy aromaticnaphthas, kerosene or other petroleum fractions, or vegetable oils;and/or stickers such as dextrins, glue or synthetic resins.

Typical wetting, dispersing or emulsifying agents used in agriculturalformulations include, for example, the alkyl and alkylaryl sulfonatesand sulfates and their sodium salts; polyhydroxy alcohols; and othertypes of surface-active agents, many of which are available in commerce.The surface-active agent, when used, normally comprises from 0.1% to 15%by weight of the herbicidal composition.

Dusts, which are free-flowing admixtures of the active ingredient withfinely divided solids such as talc, clays, flours and other organic andinorganic solids which act as dispersants and carriers for the toxicant,are useful formulations for soil-incorporating application.

Pastes, which are homogeneous suspensions of a finely divided solidtoxicant in a liquid carrier such as water or oil, are employed forspecific purposes. These formulations normally contain about 5% to about95% of active ingredient by weight, and may also contain small amountsof a wetting, dispersing or emulsifying agent to facilitate dispersion.For application, the pastes are normally diluted and applied as a sprayto the area to be affected.

Other useful formulations for herbicidal applications include simplesolutions of the active ingredient in a dispersant in which it iscompletely soluble at the desired concentration, such as acetone,alkylated naphthalenes, xylene and other organic solvents. Pressurizedsprays, typically aerosols, wherein the active ingredient is dispersedin finely-divided form as a result of vaporization of a low boilingdispersant solvent carrier, such as the Freons, may also be used.

The phytotoxic compositions of this invention are applied to the plantsin the conventional manner. Thus, the dust and liquid compositions canbe applied to the plant by the use of power-dusters, boom and handsprayers and spray dusters. The compositions can also be applied fromairplanes as a dust or a spray because they are effective in very lowdosages. In order to modify or control growth of germinating seeds oremerging seedlings, as a typical example, the dust and liquidcompositions are applied to the soil according to conventional methodsand are distributed in the soil to a depth of at least 1/2 inch belowthe soil surface. It is not necessary that the phytotoxic compositionsbe admixed with the soil particles since these compositions can also beapplied merely by spraying or sprinkling the surface of the soil. Thephytotoxic compositions of this invention can also be applied byaddition to irrigation water supplied to the field to be treated. Thismethod of application permits the penetration of the compositions intothe soil as the water is absorbed therein. Dust compositions, granularcompositions or liquid formulations applied to the surface of the soilcan be distributed below the surface of the soil by conventional meanssuch as discing, dragging or mixing operations.

The phytotoxic compositions of this invention can also contain otheradditaments, for example, fertilizers and other herbicides, pesticidesand the like, used as adjuvant or in combination with any of theabove-described adjuvants. Other phytotoxic compounds useful incombination with the above-described compounds include, for example,2,4-dichlorophenoxyacetic acids, 2,4,5-trichlorophenoxyacetic acid,2-methyl-4-chlorophenoxyacetic acid and the salts, esters and amidesthereof, triazine derivatives, such as2,4-bis(3-methoxypropylamino)-6-methylthio-s-triazine,2-chloro-4-ethylamino-6-isopropylamino-s-triazine, and2-ethylamino-4-isopropyl-amino-6-methyl-mercapto-s-triazine; ureaderivatives, such as 3-(3,5-dichlorophenyl)-1,1-dimethylurea and3-(p-chlorophenyl)-1,1-dimethylurea; and acetamides such asN,N-diallyl-α-chloroacetamide, and the like; benzoic acids such as3-amino-2,5-dichlorobenzoic acid; thiocarbamates such as S-propylN,N-dipropylthiocarbamate, S-ethyl N,N-dipropylthiocarbamate, S-ethylcyclohexylethylthiocarbamate, S-ethylhexahydro-1H-azepine-1-carbothioate and the like; anilines such as4-(methylsulfonyl)-2,6-dinitro-N,N-substituted aniline,4-trifluoromethyl-2,6-dinitro-N,N-di-n-propyl aniline,4-trifluoromethyl-2,6-dinitro-N-ethyl-N-butyl aniline,2-[4-(2,4-dichlorophenoxy)phenoxy]propanoic acid,2-[1-ethoxyimino)butyl]-5-[2-ethylthio)propyl]-3-hydroxy-2-cyclohexene-1-one,(±)-butyl-2-[4-[(5-trifluoromethyll)-2-pyridinyl)oxy]phenoxy]propanate,sodium 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoate,3-isopropyl-1H-2,1,3-benzothiadiazine-4(3H)-one-2,2-dioxide, and4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one or(4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one).Fertilizers useful in combination with the active ingredients include,for example, ammonium nitrate, urea and superphosphate. Other usefuladditaments include materials in which plant organisms take root andgrow such as compost, manure, humus, sand, and the like.

We claim:
 1. A compound having the structural formula ##STR12## wherein R is C₁ -C₁₀ alkyl; C₃ -C₈ cycloalkyl, C₃ -C₈ cycloalkylalkyl wherein the alkyl has 1 to 6 carbon atoms, C₃ -C₁₀ alkenyl, C₅ -C₈ cycloalkenyl; benzyl or mono- or di-substituted benzyl wherein the substituents are C₁ -C₄ alkyl, halogen, nitro or C₁ -C₄ haloalkyl and Y is C₁ -C₈ alkoxy, C₁ -C₈ thioalkyl, C₃ -C₆ alkenyloxy, C₃ -C₆ thioalkenyl; C₆ -C₁₀ aryloxy(thio), or C₆ -C₁₂ arylalkoxy alkoxy(thio).
 2. The compound of claim 1 wherein R is C₂ -C₆ alkyl and Y is C₂ -C₄ alkoxy, C₁ -C₄ thioalkyl, or phenoxy.
 3. The compound of claim 2 wherein R is isopropyl, isobutyl, or sec-pentyl and Y is C₂ -C₄ alkoxy, C₁ -C₄ thioalkyl or phenoxy.
 4. The compound of claim 2 wherein R is isopropyl and Y is S-methyl or S-n-butyl.
 5. The compound of claim 2 wherein R is isopropyl and Y is S-ethyl.
 6. The compound of claim 2 wherein R is sec.-butyl and Y is S-methyl.
 7. The compound of claim 2 wherein R is isopropyl and Y is ethoxy.
 8. The compound of claim 2 wherein R is isopropyl and Y is --OCH₂ CCl₃.
 9. The compound of claim 2 wherein R is isopropyl and Y is n-butoxy.
 10. The compound of claim 2 wherein R is isopropyl and Y is phenoxy.
 11. The method of controlling undesirable vegetation comprising applying to the area where control is desired an herbicidally effective amount of a compound having the structural formula ##STR13## wherein R is C₁ -C₁₀ alkyl; C₃ -C₈ cycloalkyl, C₃ -C₈ cycloalkylalkyl wherein the alkyl has 1 to 6 carbon atoms, C₃ -C₁₀ alkenyl, C₅ -C₈ cycloalkenyl; benzyl or mono- or di-substituted benzyl wherein the substituents are C₁ -C₄ alkyl, halogen, nitro or C₁ -C₄ haloalkyl and Y is C₁ -C₈ alkoxy, C₁ -C₈ thioalkyl, C₃ -C₆ alkenyloxy, C₃ -C₆ thioalkenyl; C₆ -C₁₀ aryloxy(thio), or C₆ -C₁₂ arylalkoxy alkoxy(thio).
 12. The method of claim 11 wherein R is C₂ -C₆ alkyl and Y is C₂ -C₄ alkoxy, C₁ -C₄ thioalkyl, or phenoxy.
 13. The method of claim 11 wherein R is isopropyl, isobutyl, isopentyl or sec-pentyl, and Y is C₂ -C₄ alkoxy, C₁ -C₄ thioalkyl or phenoxy.
 14. The method of claim 11 wherein R is isopropyl and Y is S-methyl or S-n-butyl.
 15. The method of claim 11 wherein R is isopropyl and Y is S-ethyl.
 16. The method of claim 11 wherein R is sec.-butyl and Y is S-methyl.
 17. The method of claim 11 wherein R is isopropyl and Y is ethoxy.
 18. The method of claim 11 wherein R is isopropyl and Y is --OCH₂ CCl₃.
 19. The method of claim 11 wherein R is isopropyl and Y is n-butoxy.
 20. The method of claim 11 wherein R is isopropyl and Y is phenoxy. 